Audio & Signal Notes

About this site

Three overlaid sine waves of different frequencies
A reference site for audio, DSP and instrumentation — tutorials with the tools built into the page.

Audio & Signal Processing Notes is a small reference site for engineers who work with audio and instrumentation signals: people measuring loudspeakers, validating a converter, decoding a frame from a logic analyser, or checking why two analysers disagree about the same tone.

What makes it different

Most calculator sites give you an input box and a number. That is exactly where the trouble starts, because a dB figure, a coherence value or a filter's attenuation is only meaningful under specific assumptions. Here, each tool is embedded in a written article that states those assumptions, derives the formula, and shows what happens when the assumptions break.

Editorial standard

  • Every formula is derived or cited, not just stated.
  • Numbers in the examples are computed, not estimated, and the arithmetic is shown so you can reproduce it.
  • Known failure modes — leakage, aliasing, insufficient averaging, reference-level mix-ups — get their own section, because that is usually what the reader came for.
  • When a topic has a genuine disagreement between conventions, the article says so instead of picking one silently.

How the tools work

All computation happens in your browser. There is no backend, no account, no upload and no queue: the page is static files, and the arithmetic is JavaScript, with the numerically intensive routines (FFT, coherence, RMS accumulation) implemented in WebAssembly. Because nothing is sent to a server, the tools also work offline once the page has loaded.

Independence and funding

The site is funded by display advertising served by Google AdSense. Advertisers have no influence over which topics are covered or what the results say, and no advertiser or manufacturer pays for a recommendation. Any commercial relationship that would affect the content would be disclosed in the article concerned. Ad cookies are described in the privacy policy.

Corrections

Engineering content goes stale and mistakes happen. If a formula, a constant or an output looks wrong, please report it via the contact page with the article name and the number you expected. Confirmed errors are corrected in the article, not quietly patched.